Hydrochloric Acid → 6-(Tert-butoxycarbonyl)-3-methoxy-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-2,4-dione

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Reaction Steps

Ethyl-4-phenoxycarbonylamino-1-tert-butoxycarbonyl-1,2,5,6-tetrahydropyridine-3-carboxylate (3.0 g) was dissolved in THF (30 ml) and O-methylhydroxylamine hydrochloride (3.2 g), triethylamine (5.35 ml) and DBU (0.3 ml) were added to the solvent, and the resultant mixture was stirred at room temperature overnight. O-methylhydroxylamine hydrochloride (3.2 g) and triethylamine (5.35 ml) were added and the resultant mixture was further stirred at room temperature for 6 hours. After production of an intermediate (urea) was confirmed by TLC, a 5 N sodium hydroxide solution (5 ml) was added and the resultant mixture was further stirred at room temperature overnight. To the reaction solution, 6 N hydrochloric acid was added, and the resultant mixture was neutralized and concentrated to obtain a precipitate by filtration. The resultant crude crystal was dissolved in methylene chloride-methanol and ethyl acetate was added to obtain a precipitate by filtration. The resultant crude crystal was purified by medium-pressure silica gel column chromatography (solvent; methanol:ethyl acetate=0:100 to 10:90). The titled compound (2.21 g) was obtained as a white powder.

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